.cla_cont1{
  padding:40px 0 0;
  background:url(../img/classroom/cont1back.jpg) 0 0 no-repeat;
  background-size:100% 100%;
}
.cla_lunbo{
  width:100%;
  height:360px;
}
.cla_cont1_dik{
  height:350px;
}
.cla_cont2{
  padding:40px 0; 
}
@media screen and (max-width:900px) {
  .cla_cont1{
    padding:20px 0;
  }
  .cla_cont1_dik{height:auto;}
  .cla_cont2{
    padding: 5px 0;
  }
}